1. Field of the Invention
The present invention is generally related to a shaft of an engine having a counterweight and a housing structure disposed at least partially around the counterweight and, more particularly, to a casing structure which defines a generally circumferential surface surrounding the counterweight in which the surface has a generally constant radius relative to an axis of rotation about which the shaft rotates.
2. Description of the Related Art
Many different products are known in which a shaft of some type is provided with an overmolded structure which encapsulates the shaft.
U.S. Pat. No. 3,725,969, which issued to Horeni on Apr. 10, 1973, describes a polishing device. A generally cylindrical molded member encapsulates an elongated driveshaft to form a solid, generally cylindrical mass for supporting a polishing cloth.
U.S. Pat. No. 4,116,575, which issued to Nakatogawa on Sep. 26, 1978, describes an encapsulated reinforcement in a moulded shaft. A coupling shaft is provided with a resilient member molded integrally therewithin during the molding process of the shaft and which is used to prevent a knob from loosening during service.
U.S. Pat. No. 4,282,810, which issued to Ellis on Aug. 11, 1981, describes a print roller. It is used for applying dye to a textile material in a predetermined pattern and is provided wherein the core of the roller, which is operatively supported in a rotatable position by a shaft, is encapsulated with a cover formed of a substantially impervious elastomeric material. Dye applicators are then bonded to the cover.
U.S. Pat. No. 4,356,605, which issued to Everts on Nov. 2, 1982, describes a crankshaft with a laminated counterweight. The counterweight comprises a plurality of substantially flat plates, each of which has a first and a second shaft mounting hole therethrough and at least one depression on one side and a boss on the other side. The plates are identical and are pressed together so that the bosses enter the depressions. Shafts are pressed into the aligned first and second holes, and an integral fully aligned torque resistant counterweight and crankshaft results.
U.S. Pat. No. 4,536,731, which issued to Kubach et al. on Aug. 20, 1985, describes an electric control motor. The motor comprises a housing made using a ferromagnetic material, a housing enclosure and a cap, a shaft rotatably disposed therein on which an armature is disposed for association with arcuate poles provided in the housing. An electromagnetic coil comprising coil portions is mounted axially with respect to the armature in coil retainers encapsulating the armature and shaft as a unit for ease of assembly in the housing.
U.S. Pat. No. 5,251,859, which issued to Cyrell et al. on Oct. 12, 1993, describes a support mount. It has a clamp with a fulcrum and a clamp plate extension. The clamp plate extension has a concave, circular toothed depression forming one half of a socket to hold a ball. The other half of the socket is formed by a jaw plate also having a concave, circular toothed depression positioned on the opposite side of the ball to the clamp plate extension. The jaw plate is positioned on the fulcrum and is kept aligned on the clamp plate by a keyway rib and slot structure. The jaw plate is tightened by a bolt or screw that passes through both the jaw plate and the clamp plate extension into a cap nut. The ball is attached to a shaft which is, in turn, attached to an ultimate support mount. Welded to and encircling the shaft is an eccentric ring. The eccentric ring and shaft are encapsulated by the ball, the ball material passing through and around the eccentric ring and shaft. In a tubular shaft, the open portion of the shaft is also left opened by the ball so that wires or other materials may be passed through the shaft. Due to the eccentric ring within the ball and encircling the shaft, enhanced support performance and strength are realized by the adjustable support mount.
U.S. Pat. No. 5,401,199, which issued to Shibata on Mar. 28, 1995, describes an outboard motor engine. Two embodiments of balancer arrangements for internal combustion engines particularly adapted for use in outboard motors are described. In each embodiment, the balancer shaft is journaled within the crankcase chamber of the engine and is driven from the crankcase from a point between its ends. Single and twin balancer shaft arrangements are disclosed.
U.S. Pat. No. 5,899,120, which issued to Leith on May 4, 1999, describes a crankshaft with laminated counterweights. A laminated counterweight for connecting the main shaft with the crank pin of a crankshaft in which the counterweight includes a pair of end laminations which are circular in shape and have a central opening dimensioned to receive the main shaft and a crank pin opening radially spaced from the central opening and dimensioned to receive the crank pin is described. A plurality of central laminations is sandwiched in between the end laminations. Each central lamination, like the end laminations, includes a central opening dimensioned to receive the main shaft as well as a crank pin opening dimensioned to receive the crank pin. A pair of cutouts is provided through each central lamination and, such cutouts being disposed on opposite sides of the radius extending between the central opening and the crank pin opening.
U.S. Pat. No. 6,237,442, which issued to Killion on May 29, 2001, describes a high value static unbalance-type balance shaft. The shaft for rotating machinery such as vehicle engines includes a bearing surface adjacent an end. The balance shaft includes a balance weight adjacent the first end and a connector portion connecting the balance weight to the other end. The connector portion has a cross-section with at least one recessed surface thereby minimizing the mass or weight of the balance shaft and optimize the material of the balance shaft.
U.S. Pat. No. 6,412,170, which issued to Happenhofer et al. Jul. 2, 2002, describes a method of manufacturing a control flap. A first sleeve and a second sleeve are put into the shaft at a predetermined axial distance apart and are pressed radially. The shaft is encapsulated between the first and second sleeve with a thermoplastic in such a way that a vane body, which has at least one aperture, is formed. The vane body is encapsulated with a sealing compound in such a way that a sealing lip is formed on the vane body at the margins.
U.S. Pat. No. 6,418,902, which issued to Ericson on Jul. 16, 2002, describes a composite full circle crankshaft counterweight. A composite crankshaft counterweight of a two-cycle internal combustion engine includes a “T” shaped counterweight surrounded by a cup-shaped retainer that holds light weight inserts against the counterweight. Together with the counterweight the inserts create a full circle that reduces the empty volume in a crankcase of a two-cycle engine.
U.S. Pat. No. 6,682,437, which issued to Killion et al. on Jan. 27, 2004, describes static unbalance-type balance shafts with axis alignment preservation. A static unbalance-type balance shaft for canceling unbalance forces of an engine include a principal bearing journal located adjacent a first end of the shaft and an outrigger bearing journal located adjacent the second end of the shaft. A first counterweight is positioned adjacent one side of the principal journal and a second counterweight is positioned on the other side of the principal journal. The balance shaft has a small third outrigger counterweight or other source of unbalance positioned adjacent the outrigger journal for maintenance of the shaft's effective plane of static unbalance within the length of the principal journal while allowing the composite center of gravity of the first and second counterweights to be shifted away from the outrigger unbalance, for the purpose of improving the stability of shaft operating shape at the outrigger journal end of the shaft across the entire range of operating speeds.
U.S. Pat. No. 7,273,028, which issued to Ho on Sep. 25, 2007, describes a noise suppressing mechanism for a balance gear of engine crankshaft. A noise suppressing mechanism for a balance gear system of an engine crankshaft is described. The balance gear system includes a primary gear, a secondary gear, and a torsional spring and is fit on a balance shaft. The noise suppressing mechanism includes a circular flange formed on the primary gear and the secondary gear forms a central bore rotatably fit over the circular flange for free rotation about the circular flange with respect to the primary gear. The torsional spring is arranged between the primary and secondary gears. The primary gear forming a securing hole in which a stem section of a limiting pin is received and fixed. The secondary gear forms a through hole in which a head section of the limiting pin is accommodated with a gap formed between the head section and an inside diameter of the through hole. The gap allows for a limited angular shift of the secondary gear with respect to the primary gear. Such an arrangement provides a noise suppressing mechanism having less number of parts and being ready to assemble.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.